1.Definition: appealing to the mind
"A serious book"
2.Definition: causing fear or anxiety by threatening great harm
"A serious wound", "A serious turn of events"
4.Definition: concerned with work or important matters rather than play or trivialities
"A serious student of history", "A serious attempt to learn to ski", "Gave me a serious look", "A serious young man", "Are you serious or joking?", "Don't be so serious!"
5.Definition: of great consequence
"Marriage is a serious matter"
6.Definition: requiring effort or concentration; complex and not easy to answer or solve
"Raised serious objections to the proposal", "The plan has a serious flaw"